Nodular tertiary syphilis mimicking granuloma annulare.

We describe a 47-year-old man with annular plaques on the arms and torso that were treated as granuloma annulare, based on clinical and histopathologic findings. Exacerbation of the lesions during treatment with topical corticosteroids prompted a search for an infectious cause, which proved to be syphilis in the tertiary stage. The clinician should maintain a high index of suspicion for syphilis in the differential diagnosis of unusual annular skin lesions in a patient with noncaseating granulomas seen on skin biopsy.